Humic substance - acids (humic, ulmic, fulvic), which are part of the dark colored aqueous humus, which is formed during decomposition of dead plants and humification. They are contained in soil humus, peat and brown coal.

Humic acids are a complex mixture of high molecular weight natural organic compounds formed during decomposition of dead plants and their subsequent humification (biochemical transformation of products of decomposition of organic residues into humus with the participation of microorganisms, water and oxygen). In the dry state it is a non-movable amorphous dark brown powdery product. Humic acids are part of the organic mass of peat, coals, some soils and lignosulfonate (a by-product of wood processing), from which they are extracted by treatment with weak aqueous alkaline solutions.

Humic acids affect organoleptic properties of water (smell, color), accelerate metal corrosion, have a negative effect on the development of water microorganisms, affect the chemical composition of water (reduces oxygen content, affects ionic and phase equilibria).

Humic substances (from the Latin humus - earth) were first isolated in 1786 by the German scientist Franz Aschar from peat. Later, soils, sapropel, brown coals and lignosulfonate became the sources for obtaining a number of humic acid-based preparations. In Russia humic preparations made from peat, brown coal, sapropel and lignosulphonate have been used for feeding farm animals and plants since the beginning of the second half of the XX century up to the present time. Humate-based preparations (potassium/sodium humate with microelements, GSN-2004, Humate+7, Guvitan-S, Vitapdin, Hermivit, Humivit, Torphogel) contain amino acids, polysaccharides, monosaccharides, carbohydrates, vitamins, macro- and microelements, hormone-like substances. They belong to high-molecular compounds and are characterized by stability and polydispersity. Humates have sorption, ion exchange and biologically active properties.

Humic acids form strong compounds with metal ions, which determines their global geochemical role. The different solubility groups of humic acids, fulvic acids and humic acids, have opposite geochemical functions. Fulvic acids increase the migration ability of elements in the Earth's crust, while humic acids represent a powerful geochemical barrier. The interaction with humic acids is the initial step in the chain of processes leading to the accumulation of noble metals in carbonaceous rocks and the formation of ore deposits.